Jet propulsion systems are mechanisms that generate thrust by expelling mass at high speed. This principle is based on Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. Commonly used in aircraft and spacecraft, these systems typically involve engines that burn fuel to produce hot gases, which are then expelled through a nozzle. There are various types of jet propulsion systems, including turbojet, turbofan, and rocket engines. Each type has its own design and application, with turbofan engines being popular in commercial aviation for their efficiency and quieter operation. In contrast, rocket engines are used in space exploration, where they operate in the vacuum of space.